Exercise stress ECG interpretation practice: new ST elevation

Quiz yourself: ST elevation on an exercise stress ECG

Your patient, a 57-year-old male, is three minutes into a Bruce protocol stress test. No symptoms, blood pressure is rising appropriately, and then new 1.5 mm ST elevation appears in V2 and V3, with no prior Q waves in those leads. What do you do?

a. Keep going. The patient is asymptomatic and hasn't reached target heart rate.

b. Hold the current stage and repeat the 12-lead in one minute.

c. Keep going, but stop if chest pain develops.

d. Stop the test.

Check your answer

The answer is d: stop the test. One millimeter or more of ST elevation in a lead without prior Q waves can indicate severe ischemia or coronary spasm. It's rare but very serious. Symptoms aren't required. The ST elevation alone is enough to stop the stress test and calls for urgent evaluation, even if the patient feels fine.

"New" matters, too. Some patients have mild ST elevation in V2 at rest from early repolarization, which isn't a concern on its own. But exercise-induced ST elevation that wasn't on the resting ECG means stop.

Weighing the other choices

a. Keep going to reach target heart rate. Once diagnostic ischemic changes are present, the clinical question has already been answered. Continuing adds risk without adding useful information.

b. Hold the stage and repeat the 12-lead. Exercise-induced ST elevation isn't a wait-and-see finding. It calls for immediate termination of the test.

c. Keep going until symptoms appear. Waiting for chest pain only delays a stop that's already indicated.

Other reasons to stop an ECG exercise stress test right away

ST elevation isn't the only stop-now signal. Stop the test if the patient develops:

• Moderate to severe chest pain, especially if it feels like the pain that brought them in
• Severe shortness of breath, wheezing, or signs of low oxygen
• Unsteadiness, poor coordination, or new neurological symptoms such as confusion, dizziness, or ataxia
• A drop in systolic blood pressure of more than 10 mmHg while the workload is still increasing, especially when paired with symptoms
• Systolic blood pressure above your lab's safety threshold, often around 250 mmHg, but always guided by your local protocol
• More than 2 mm of ST depression
• New conduction blocks or complex ventricular arrhythmias
• Sustained ventricular tachycardia, a growing number of premature ventricular contractions (PVCs), a new atrioventricular (AV) block, or any rhythm that makes you uncomfortable about their stability

Also stop if the patient asks you to, or if you can no longer accurately monitor the ECG or blood pressure.

Interpreting stress test ECGs: not every finding means stop

• PVCs in a stable, asymptomatic patient with no ischemic changes don't require you to stop immediately, but they do need close monitoring. If the arrhythmia becomes sustained or more complex, or the patient develops symptoms, that changes things.
• Fatigue that rises gradually with workload is a normal response to exercise.
• Mild upsloping ST depression is often nonspecific and isn't a stopping criterion.

Key takeaway

New ST elevation in leads without prior Q waves is enough on its own to stop an exercise stress test, even if the patient feels fine and hasn’t reached target heart rate.
 

Want more exercise stress ECG interpretation practice?

Our newly updated Exercise Stress ECG Essentials Workshop has 22 cases to work through. Decide whether to modify the protocol, read the tracings stage by stage, choose whether to continue or stop, and interpret the results. In the final cases, you'll use stress test and cardiopulmonary exercise test findings to build a safe exercise prescription.